diff --git a/parso/python/normalizer.py b/parso/python/normalizer.py
index 5b132af..b0c24c4 100644
--- a/parso/python/normalizer.py
+++ b/parso/python/normalizer.py
@@ -181,6 +181,20 @@ class ErrorFinder(Normalizer):
                 # foo(x for x in [], b)
                 message = "Generator expression must be parenthesized if not sole argument"
                 self._add_syntax_error(message, node)
+
+            ###
+            arg_set = set()
+            for argument in node.children[::2]:
+                if argument.type == 'argument' and argument.children[1] == '=':
+                    kw_only = True
+                    keyword = argument.children[0]
+                    if keyword.type == 'name':
+                        if keyword.value in arg_set:
+                            # f(x=1, x=2)
+                            message = "keyword argument repeated"
+                            self._add_syntax_error(message, keyword)
+                        else:
+                            arg_set.add(keyword.value)
         elif node.type == 'atom':
             first = node.children[0]
             # e.g. 's' b''
@@ -232,9 +246,15 @@ class ErrorFinder(Normalizer):
             else:
                 self._add_syntax_error(message % type_, lhs.parent)
         elif node.type == 'argument':
-            if node.children[1] == '=' and node.children[0].type != 'name':
-                message = "keyword can't be an expression"
-                self._add_syntax_error(message, node.children[0])
+            first = node.children[0]
+            if node.children[1] == '=' and first.type != 'name':
+                if first.type == 'lambdef':
+                    # f(lambda: 1=1)
+                    message = "lambda cannot contain assignment"
+                else:
+                    # f(+x=1)
+                    message = "keyword can't be an expression"
+                self._add_syntax_error(message, first)
 
         yield
 
diff --git a/test/test_python_errors.py b/test/test_python_errors.py
index 82f5aa5..f3da805 100644
--- a/test/test_python_errors.py
+++ b/test/test_python_errors.py
@@ -91,6 +91,8 @@ def test_indentation_errors(code, positions):
         '*star,: int',
         'a, b: int = 3',
         'foo(+a=3)',
+        'f(lambda: 1=1)',
+        'f(x=1, x=2)',
 
         # IndentationError
         ' foo',